initial jolokia collector rewrite

This is a collector that we use internally for gathering metrics from Java applications (primarily Cassandra) via the Jolokia agent HTTP interface. (http://www.jolokia.org/agent/jvm.html)
We've found it a lot easier to grab large numbers of metrics in a single request using Jolokia than with direct JMX access.

The collector has recently been rewritten to enable fetching metrics from multiple agents.
It does require the pyjolokia library to function, but this is checked for on startup and mentioned in the log.